A128826 a(n) = 10^(2n-1) minus largest square less than 10^(2n-1).

1, 39, 144, 1756, 49116, 484471, 4175271, 38053824, 10649244, 1064924400, 43246886799, 529955487744, 2399106211776, 50173961567511, 590207432515431, 2099745368512359, 20237877241133151, 126421128012287511

Offset: 1

Author

Zak Seidov, Apr 12 2007

Keywords

• nonn

Comments

For even indices a(2k) = 2*10^k-1, hence only odd powers of 10 are considered in this sequence.

Examples

			a(1) = 1 because 10 - 3^2 = 1.
a(2) = 39 because 1000 - 31^2 = 39.
a(3) = 144 because 100000 - 316^2 = 144.
		

Links

• Hugo Pfoertner, Table of n, a(n) for n = 1..500

Crossrefs

Cf. A061433, A051221.

Programs

Mathematica

Table[10^n-Floor[(10^n-1)^(1/2)]^2,{n,1,40,2}]

Formula

a(n)=10^(2n-1)-A061433(2n-1).

a(n) = 10^(2*n-1) - floor(sqrt(10^(2*n-1)))^2.